The UK has experienced a sudden rise in extended-spectrum ß-lactamase (ESBL) rates, largely due to the appearance and spread of Escherichia coli producing CTX-M-15 type ß-lactamase. The British Society for Antimicrobial Chemotherapy organized two update meetings during 2004 to report and discuss the recognition, clinical diagnosis, treatment and control of bacteria producing these ß-lactamases. This paper reports the data and reviews made by contributors to the conferences. The historical distribution and emergence of ESBLs was reviewed along with the emergence of plasmid-mediated CTX-M ESBLs following their mobilization from the chromosome of Kluyvera spp. The first significant outbreak of CTX-M producers in the UK occurred in 2001 and involved Klebsiella pneumoniae with CTX-M-26 at one site, but by 2003, cloned and diverse E. coli with CTX-M-15 were widespread, with Shropshire one of the most affected regions. The specific experience in Shropshire was reported on and a comprehensive review made of the level of awareness of the need for ESBL detection in laboratories in England and Wales, together with a description of the variety of methods that may be applied, with recommendations for optimal methodology. The increased mortality associated with inappropriate treatment of infections caused by ESBL-producing strains was highlighted, together with discussion on potential control of cross-infection. The meeting concluded that the CTX-M genes have now become widespread in not only E. coli but other Enterobacteriaceae in the UK and this will represent a substantial threat to both the treatment of infections caused by these bacteria in the community and within hospitals.